Mobile and/or wireless electronic devices are becoming increasingly popular. For example, mobile telephones, portable media players and portable gaming devices are now in wide-spread use. In addition, the features and accessories associated with certain types of electronic devices have become increasingly diverse. To name a few examples, many electronic devices have cameras, text messaging capability, Internet browsing capability, electronic mail capability, video playback capability, audio playback capability, image display capability and handsfree headset interfaces. Exemplary accessories may also include headsets to provide sounds, e.g., music or other audio content, music and video input players, etc.
Headphones, also sometimes referred to as earphones, are a type of headset (also referred to as listening device) that have been used to listen to audio content or material, e.g., sounds, such as music, lectures and so on, provided from various electronic devices, such as, for example, stationary music players, radios and the like, and portable electronic devices, such as, for example, mobile phones, Sony Walkman players, and so on. Headphones typically have used speakers that are positioned over the ears of a user to convey audio content to the respective ears and a support bar on which the speakers are mounted; the support bar fits over the user's head to hold the speakers in generally fixed relation to each other and in place over the user's ears, as is well known. The modern trend has been to reduce the size of such portable electronic devices and also to reduce the size of listening devices used to listen to audio content provided from such portable electronic devices. An example of a modern small listening device is the ear bud; for example, two ear buds (sometimes referred to as ear bud listening devices), each placed in a respective ear of a user, may be used to convey audio content directly to the user's ears. Ear buds do not require a physical mechanical connection between them, such as the physical connection and mechanical support that typically is provided by a support bar used for conventional headphones.
In many cases it is desirable to know information representing or indicating the direction and/or rotation of the head of a user of a portable electronic device, such as, for example, a mobile phone, music or other sound playing device, personal digital assistant, game device and so on. This information may be useful for gaming, virtual reality, augmented reality, and so on, as audio content and navigation information is heard by a user. Some modern mobile phones have direction sensors, but the mobile phone will not provide information pertaining to a user's head facing direction or rotation information, since usually it does not track movements of the user's head. Some virtual reality display systems that provide both image and audio outputs have used headsets that include head tracking mechanisms to alter images and/or sounds in relation to the direction of the user's head. One example of a sensor to use for tracking rotation of the head is a gyroscope. However, although a gyroscope may be useful mounted on a conventional headset, it is problematic for use in ear buds because gyroscopes are large, expensive and consume a substantial amount of power, e.g., as compared to the relatively small size of ear buds and their relatively low cost small power requirements. A magnetometer provides absolute direction compared to a geomagnetic field, but the strong magnetic field produced by the speaker in an ear bud would saturate the magnetometer.
It has been a problem to obtain angular motion information of the head of a user while using small ear pieces, e.g., earbuds, that are not mounted relative to each other on a fixed support like conventional earphones. Quite small earpieces, e.g., earbuds, may simply be attached to and relatively loosely dangle at the end of an electrical cable. Although such earbuds are convenient for listening to sounds from a portable electronic equipment and easily can be stored, they have not previously been able to obtain features of heavier earphone systems with rigid connection bars between speakers and gyroscopic type direction monitoring/obtaining devices that can use the direction information for various purposes, e.g., to obtain three-dimensional stereophonic audio output, changing of audio output in response to changes in direction, and so on.